As a mobile device is generally used, various methods of using the mobile device have been suggested. Except a voice call, the most commonly used service for a user of the mobile device is text message transmission service such as a SMS (Short Message Service). The text message transmission service allows information to be transmitted readily and quickly to the other party at low costs. A mobile device is equipped with a keypad having a limited number of keys, and, thus, it is very complicated to input characters by using the keys. Particularly, if plural characters are assigned to a single key, a required character is selected by pressing a keypad several times.
Recently, character input has been required in various input/edit modes, and, thus, it becomes common to select and input more characters than a physical number of keys on a keypad by using a fixed number of keys.
FIG. 1 shows a conventional mobile device for inputting alphabetic characters.
Referring to FIG. 1, a conventional mobile device 10 includes a function key section 20 and a keypad section 30.
The function key section 20 includes one or more function keys such as a menu key, a search key, a send key, an end key, and direction keys.
The keypad section 30 has a basic configuration of a 4 by 3 matrix of twelve keys including ten numeric keys 0 to 9 and two control keys labeled “*” (hereinafter, referred to as “* key”) and “#” (hereinafter, referred to as “# key”) and each of the numeric keys 1 to 9 is also assigned three or four alphabetic characters in order to input alphabetic characters.
In the keypad of the conventional mobile device, a single key is assigned three or four alphabetic characters. Therefore, in order to repeatedly input the same alphabetic character or successively input alphabetic characters assigned on a single key, a user displays one of the alphabetic characters by a manipulation of the key and needs to wait for a predetermined waiting time, such as about one second, required for the displayed alphabetic character to be recognized as an input character, and then inputs the next alphabetic character by pressing the same key again.
By way of example, in order to input alphabetic characters “ABCD”, with a predetermined time, such as about one second, after the user presses the numeric key “2” once, the first alphabetic character “A” is input and with a predetermined time, such as about one second, after the user presses the numeric key “2” successively twice, the second alphabetic character “B” is input and then the third alphabetic character “C” is input by pressing the numeric key “2” successively three times and finally, the fourth alphabetic character “D” is input by pressing the numeric key “3” once. The user can be informed that such a waiting time elapses by a flicker or a movement of a cursor.
That is, it takes the waiting time of about two seconds to input the alphabetic characters “ABCD”. The waiting time of about two seconds may be longer when a long sentence is input. A user good at typing keys may feel like that such a waiting time is a much longer and may be frustrated at several halts while inputting characters.
If the keypad is pressed more quickly than the waiting time, an unwanted character is input.
In order to ease such inconvenience in inputting characters, Korean Patent Laid-open Publication No. 10-20002-0007852 discloses “a method of inputting characters of a mobile device and a mobile device using the same method” in which plural “shift” keys correspond to an assignment order of characters on a single key and a certain character is input by pressing one of the “shift” key corresponding to an assignment order of the character before inputting the character.
Although this disclosure suggests a technique of selecting and inputting each of the characters on the single key by using the plural “shift” keys, in order to input any one of three or four alphabetic characters on the single key, a separate “shift” key is additionally needed, which becomes a burden for design of a mobile device.
Further, in the above-mentioned method, a user needs to recognize an assignment order of a character and needs to select and input one of the plural “shift” keys every time before a character is input. Therefore, it may take a longer time for a user who is not good at typing keys to input characters.